吃有机肉、喝有机奶的人也许真的更健康

Organic meat and milk differ markedly from their conventionally produced counterparts in measures of certain nutrients, a review of scientific studies reported on Tuesday.

周二（2月9日），一项科学研究综述报告，有机肉类和牛奶在某些营养成分上与通过常规方式生产的同类产品间存在明显差异。

In particular, levels of omega-3 fatty acids, beneficial for lowering the risk of heart disease, were 50 percent higher in the organic versions.

尤其是，有机产品中有益于降低心脏病风险的ω-3脂肪酸的水平比普通产品高出50%。

“The fatty acid composition is definitely better,” said Carlo Leifert, a professor of ecological agriculture at Newcastle University in England and the leader of an international team of scientists who performed the review.

However, the question of whether these differences are likely to translate to better health in people who eat organic meat and drink organic milk is sharply disputed.

然而，上述差异是否代表着吃有机肉类、喝有机牛奶的人更为健康呢？人们对此仍有尖锐的争议。

“We don’t have that answer right now,” said Richard P. Bazinet, a professor of nutritional sciences at the University of Toronto who was not involved with the research. “Based on the composition, it looks like they should be better for us.”

The two new scientific papers, published in The British Journal of Nutrition, are not the result of any new experiments, but instead employ a statistical technique called meta-analysis that attempts to pull robust conclusions out of many disparate studies.

这两篇新的科学论文发表在《英国营养学杂志》(The British Journal of Nutrition)上，它们并没有介绍什么新的实验结果，而是采用了一种名为荟萃分析的统计技术，试图从众多不同的研究中得出强有力的结论。

They are certain to further stir a combative debate over whether organic foods are healthier. Some scientists assert that organic and conventional foods are nutritionally indistinguishable, and others find significant benefits to organic. Many people who buy organic food say they do so not for a nutritional advantage, but because of environmental concerns and to avoid pesticides.

The higher levels of omega-3, a type of polyunsaturated fat, arise not from the attributes usually associated with organic food — that the animals are not given antibiotics, hormones or genetically modified feed — but rather from a requirement that animals raised organically spend time outside. Organic milk and beef come from cattle that graze on grass, while most conventional milk and beef come from cows subsisting on grain.

Most of the same changes would be observed in conventionally raised animals that also grazed for the majority of their diet, the scientists said.“For once, this is a pretty simple story,” Dr. Benbrook said.

科学家们表示，如果常规饲养的动物也以吃草为主，那么在它们身上也能发现很多相同的改变。“这样一来，问题就变得简单了，“本布鲁克博士说。

The review of comparisons of organic and conventional milk analyzed all 196 papers the scientists found. Because studies of meat are sparser, they could not look at just one type of meat like beef or pork. Instead, they did one analysis of the 67 papers they found for all types of meat. “Only if you throw them all in one pot can you do a meta-analysis,” Dr. Leifert said.

Two years ago, Dr. Leifert led a similar review for fruits and vegetables that found organic produce had higher levels of some antioxidants and less pesticide residue than conventionally grown crops.

两年前，莱费特博士领导了一项关于水果和蔬菜的类似综述，发现与用常规方法种植的作物相比，有机农产品中某些抗氧化剂的水平较高，农药残留较少。

Nutrition experts broadly agree that omega-3 fatty acids in food offer numerous health benefits. When the United States Department of Agriculture revised its dietary guidelines in 2010, it urged people to eat more seafood, which is rich in omega-3.

营养专家普遍认同，食物中的ω-3脂肪酸具有多种健康效益。美国农业部(United States Department of Agriculture)在2010年修订其膳食指南时，呼吁人们多多食用富含ω-3脂肪酸的海产品。

Omega-3 is much more prevalent in grass than in grain, which is why organic livestock and milk also contain higher levels. “Lo and behold, we altered in some fundamental ways the nutrient intake of these animals and hence the nutrient composition of the products that we derive from those animals,” Dr. Benbrook said.

The new analysis found that levels of another polyunsaturated fat, omega-6, were slightly lower in organic meat and dairy. Omega-3 and omega-6 are essential for the functioning of the human body, which can make neither. But some have argued that a skewing toward omega-6 has become unhealthy.

Centuries ago, people ate roughly equal amounts of the two fatty acids. Today, most Americans eat more than 10 times as much omega-6, which is prevalent in certain vegetable oils and thus also fried foods, as omega-3.

In an email, Dr. Walter C. Willett, the chairman of the nutrition department at the Harvard T.H. Chan School of Public Health, said the differences between organic and conventional beef were trivial, and the amount of saturated fat in both were high.

哈佛大学公共卫生学院(Harvard School of Public Health)的营养系主任沃尔特·C·威利特(Walter C. Willett)博士在一封电子邮件中写道，有机和常规牛肉之间的差异微不足道，而且两者中的饱和脂肪含量均很高。

“Far greater, and beneficial, differences in fatty acids are seen if poultry and fish replace red meat,” Dr. Willett said.

“如果用禽肉和鱼肉来代替红肉，你会发现更大、更有益于健康的脂肪酸差异，”威利特博士如是说。

A shortcoming of the recommendation to eat more fish is that if everyone followed it, the rivers, oceans and lakes would be emptied of fish. Dr. Bazinet of the University of Toronto said perhaps encouraging people to switch to organic meats and milk would be “a way to kind of get at them with the foods they’re already eating.”

Dr. Bazinet said observational studies suggested that adding 200 milligrams a day of omega-3s to an average diet should yield health benefits. Switching to organic beef would add about 50 milligrams. “Eating one grass-fed beef serving per day is not going to do it,” he said.

But if combined with a couple of glasses of organic milk, “it should make a difference,” Dr. Bazinet said. “That would be the hypothesis.”

但是，如果再喝上一两杯有机牛奶的话，“应该就有用了，”巴齐内博士说。“假设上是如此。”

Scientists are now trying to examine the health question more directly.

现在科学家们正试图以更直接的方式来探讨这些健康问题。

Dr. Leifert cited several studies that indicated that infants of mothers who ate organic fruits and vegetables were less likely to contract some diseases. He is also conducting experiments to see if rats fed organic foods are healthier. So far, he said, it appears that crop pesticide residue does have measurable effects on the rats’ hormones.